Miconazole, fenarimol and compounds with similar modes of action will be studied to determine effects on oxidative demethylation of sterols and on mixed function oxidation of pesticides, model substrates and medicinal chemicals in microsomal systems from Ustilago maydis. Other studies will be conducted with tricyclazole; 4,5-dihydro-4-methyltetrazolo(1,5a) quinazolin-5-one and 1,2,5-6, tetrahydro-4H-pyrrolo(3,2,1-i,J)quinolin-5-one to relate specific inhibition of polyketide melanin biosynthesis by the compounds in Pyricularia oryzae to the mechanism of disease control. Similar studies will be conducted with non-pathogenic mutants of P. oryzae genetically defective in melanin biosyntheses at the site blocked by the above mentioned chemicals.